This invention relates to temperature control systems and, more particularly, to a system for selectively controlling permissible temperature ranges in each of a plurality of remote zones from a control location for the purpose of conserving energy by controlling heating or cooling in such remote zones.
It is, of course, known that the amount of energy utilized for transferring heat to a house or other zone such as an area or room within a larger structure can be conserved if the temperature is permitted to vary over a greater range in response to external environmental considerations. For example, if heating is not employed until the temperature drops to 50.degree. F. (10.degree. C.) or, by the same token, if air conditioning is not employed until the temperature in a zone reaches some upper limit, such as 85.degree. F. (29.4.degree. C.), much less energy will be consumed than would be the case if the temperature were permitted to vary only about a much narrower range such as from 65.degree. F. (18.3.degree. C.) to 74.degree. F. (23.3.degree. C.) through transfer of heat to or from the zone. Temperature is quite often permitted to vary only in a rather narrow range such as the latter.
It will be immediately recognized that it is the usual practice in both domestic and commercial areas to permit the temperature rarely to fall below relatively warm temperatures such as 65.degree. F. (18.3.degree. C.) or even 70.degree. F. (31.1.degree. C.), for example. On the other hand, it is conventional practice to employ air conditioning for cooling dwellings and commercial areas when the temperature rises only slightly above that which is considered warm.
Needless to say, the overriding humanist and self-survival considerations of conserving energy in view of the now well recognized shortage of available sources of energy clearly mandate that worldwide efforts to conserve energy be accelerated and implemented whenever and wherever possible. Thus, where a zone or dwelling is to be unoccupied over a considerable period of time, energy should not be utilized wastefully and needlessly for maintaining the temperature in such zone or dwelling within a narrow range of temperatures. For example, in a hotel or motel or other commercial building where a room or other zone is unoccupied, it is desirable to permit the temperature in the zone to fall to a quite low value such as 50.degree. F. in the winter and to permit rise in the temperature during a warm season, to a very high temperature, such as 85.degree. F. since such extremes of temperatures are unlikely to cause damage to inanimate objects within such zone and will cause only trivial discomfort to a person who may enter or transit the zone for a brief period, such as maintenance employees.
Yet, it is desirable when there is occupancy of such zone to permit a more modest temperature variation, i.e., over a range of temperatures not so extreme as to cause great discomfort to occupants. But even where the zone is to be occupied, it may be desirable to prevent heating or cooling when temperatures are within a band or range which is reasonably tolerable to the occupants. Consequently, it may be desirable to place limits on the temperature which can be maintained by energy-consumptive heat transfer such as by operating a furnace or airconditioner for the purposes of either cooling or heating. Even where such limits are imposed, it may nevertheless be desirable to permit occupants to exercise a degree of control over temperatures in the zone, so long as the limits are not exceeded.
It is known to provide adjustable or multiple functional thermostat switches which are clock-controlled so that different thermostats govern temperature regulation at differing times of the day. Remote operation of thermostats has also been proposed utilizing radio or dedicated circuit signalling. It is possible also to manually vary the temperature setting of such thermostats or manually select alternate theremostats so as to provide for permitting variation of temperature over a greater range when a zone is unoccupied. However, it must be recognized that in a commercial establishment such as a motel or hotel in which there are many rooms, and perhaps even hundreds or thousands of rooms, it is most inconvenient and as a commercial matter economically impractical to manually vary permissible temperature ranges by adjustment, for example, of the thermostats in each room by maintenance personnel or the like when a zone becomes unoccupied, as where a guest checks out of a room.
While a hotel or motel room cleaning person can manually change a room thermostat when the room is cleaned after a guest checks out, resetting a conventional thermostat may permit only a modest energy saving. Moreover, energy wasting cooling and/or heating may continue until the room is visited by such cleaning person. Moreover, the room will be uncomfortable for a period after occupancy until a guest or hotel personnel can reset the room thermostat.
Accordingly, it is desirable to provide a system for selectively controlling permissible temperature ranges in each of a plurality of such remote zones from a central control location. It is also advantageous to provide a system of such character that it can be installed and placed in operation without having first to provide for the expensive and time consuming installation of conductors, cables or the like between the central facility and zones in which temperature variations are to be controlled. Heretofore, such a possibility has not readily been achievable without the use of so-called dedicated circuits, multiplexing, coding-decoding circuits or a radio remote control, all of which suffer from complexity, great expense, and inconvenience or difficulty of installation.
A related factor which is of concern in determining zone temperature regulation particularly in commercial structures such as hotels, motels and large buildings has to do with the rate at which energy is being consumed. If electrical power is utilized for heating or cooling, it is conventional to purchase such power at rates determined according to a peak demand rate structure. In this regard, it will be understood that if electrical power is used at a rate which is greater than the peak demand, the rate for which such power is purchased from the power utility may be increased substantially or penalties assessed. Such a stepped or penalty imposing rate structure is now or may soon be applicable to other forms of energy purchased for cooling or heating purposes such as gas, oil or steam. If, for example, the use of electrical power approaches the authorized peak demand for a power consumer, it is desirable that steps be taken to limit the amount of electrical power or other forms of energy so utilized or even to cut back on consumption of energy to avoid having to incur the higher rates or penalties associated with exceeding authorized levels of usage.
In addressing the foregoing concerns it is important to keep in mind that a system for conserving energy through selective control of permissible temperature ranges in remote locations must be accomodative of and compatible with a variety of heating and air conditioning systems with different types of units possibly utilized at the various remote zones. To illustrate, a commercial establishment (such as a motel) may utilize a plurality of different kinds of heating and/or cooling systems at various locations. For example, some rooms may have "through-wall, " e.g., through-window units, of a self-contained nature in which an independent unit is used for cooling or heating but has no connection with a central system, other than being supplied by AC power. Other rooms may have local fan/coil units interconnected with a central source of heating a cooling fluid such as steam or air but which units are under the control of a room thermostat.